Sean Owen created CRUNCH-575:
--------------------------------
Summary: DistributedPipeline temp dir choice can collide with
itself
Key: CRUNCH-575
URL: https://issues.apache.org/jira/browse/CRUNCH-575
Project: Crunch
Issue Type: Bug
Components: Core
Affects Versions: 0.12.0
Reporter: Sean Owen
Assignee: Josh Wills
Priority: Minor
We've observed that Crunch jobs can fail because the output temp dir already
exists:
{code}
2015-04-02 04:45:49,208 INFO
org.apache.crunch.hadoop.mapreduce.lib.jobcontrol.CrunchControlledJob:
org.apache.hadoop.mapred.FileAlreadyExistsException: Output directory
/tmp/crunch-686245394/p2/output already exists
at
org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:132)
{code}
One possible cause is the choice of random directory name, which is based on a
random nonnegative 32-bit int. The chance of collision is more than 50% at
about 55,000 temp dirs, which is not unimaginable.
A suggested fix, at least for that theoretical cause, is to generate a much
larger random value. 64 bits should put this firmly in the realm of extremely
improbably (billions, not tens of thousands).
(HT [~wilfreds] / CC [~tomwhite])
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